EDR,

I am afraid that I beg to differ. You certainly may question the value
of an "average" TBO to decision-making, but you can track the numbers
quite accurately (assuming correct reporting). It would really only
take the cooperation of a small number of overhaul shops, some A&P
mechanics and such.

In the same way, one could question the value of the accident rate of
the "average" GA pilot. Granted that all of us are above average
(apologies to Garrison Keillor), but such statistics can be useful
starting points, for example, to see if trends are improving or if a
given measure is worthwhile. Similarly, average disease mortality rates
are useful for medical treatment, despite no person being average.

I do not mean to beat a dead horse, but I really think it would be a
good idea, from an engineering perspective, to collect and report this data.

-Sami
N2057M, Piper Turbo Arrow III

EDR wrote:

There is too much variability in operation to accurately track
reliability/dependability of an engine.
TBO comes from the manufacturer's test stand and flight test data under
controlled conditions. Same place the 55/65/75% power data comes from.